UC Riverside

While creatine levels in skeletal muscles can be enhanced by exogenous creatine supplementation, the elevation of creatine levels in the brain with oral creatine administration remains a challenge due to a lack of effective creatine transportation through the blood-brain barrier (BBB). As consequence, intranasal administration has been established as a method to bypass the blood-brain barrier and deliver drugs directly to the brain. In our studies, we focused on using intranasal delivery to bypass the BBB and deliver creatine to the brain. Our first objective was to use magnetic resonance spectroscopy to measure creatine accumulation in the brain after a 14-day period of intranasal administration. The spectra showed that the brain creatine/choline ratio was significantly increased after creatine administration. This proved the accumulation of exogenous creatine in the brain. In the second objective, we studied the effects of intranasal creatine administration on wild-type rats and evaluated the cognitive performance after administration via the Barnes maze experiments. This study demonstrated that intranasal creatine administration can improve the performance of rats in the Barnes maze. The results of biochemical assays showed that administration of creatine can increase the creatine content in the rat brain. Despite the success of intranasal administrations, there are still drawbacks, especially when it comes to pH and solubility. To address the solubility limitation of creatine concentration per unit volume and ensure a pH value close to neutral, we assembled creatine microparticles. We tested the characteristics of these creatine microparticles, including size distribution, functional group composition, assembly rate, stability, and cytotoxicity. In vitro permeability measurements indicate creatine microparticles are permeable to human respiratory epithelial cells. Overall, we developed methods to evaluate efficacy of intranasal creatine administration in vivo and methods to evaluate characteristics and permeability of creatine microparticles in in vitro drug delivery models. Our experiments indicate intranasal administration of creatine can improve wild type rats’ cognitive performance in Barnes maze and increases creatine content in the brain. Moreover, creatine microparticle suspensions were proven to exceed the limits of creatine solubility. This approach enables the delivery of creatine intranasally beyond their solubility limits without significant cytotoxicity and alteration of cell layer integrity.